Polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) alloy resins can have heat resistance and impact strength of a polycarbonate resin (PC) and processability and chemical resistance of an acrylonitrile-butadiene-styrene (ABS), thereby providing excellent processibility and mechanical properties. Accordingly, the PC/ABS alloy resins may be utilized in various applications including not only electric and electronic products, such as monitor housings, hard disks, printers, notebook batteries, and the like, but also automobile components, such as door handles, bumpers, instrument panels, and the like.
When PC and ABS resins are kneaded or mixed when preparing a PC/ABS alloy resin, ABS is present in the form of a rubber incorporated into a styrene-acrylonitrile (SAN) domain. The alloy resin can undergo deterioration in gloss or appearance according to the domain size, and deterioration in thermal properties according to the amount of ABS.
To address this problem, methods for dispersing ABS using grafted ABS having high rubber content upon kneading ABS with PC have been suggested. However, despite improvement in dispersibility of ABS in PC, such methods have a problem of local deformation of appearance caused by modification of rubber in ABS, dispersion of ABS resin around a site, such as a gate, in which a huge difference in fluidity occurs during injection molding, and the like.
Non-halogen-based flame retardant PC/ABS resins are often used as exterior materials for large flat televisions, which require high coloring and high gloss appearance. Deterioration in appearance of such products made of flame retardant PC/ABS resins can cause variation in surface roughness due to GAS materials, problems in dispersion of ABS resin, and modification of rubber in ABS resin.
Despite compatibility between PC and ABS, PC and ABS are present in two phases, in which the ABS phase mainly constitutes domains. The size of domains and the degree of dispersibility of the domains may vary depending on injection molding conditions. Non-uniform dispersibility of PC and ABS results in non-uniform index of refraction of PC and ABS, causing some phenomena, such as sagging mark and/or smearing of ABS or PC, on surfaces of molded articles.
In order to address such deterioration in appearance, PC can be mixed with ABS having a low content of rubber. In this case, the amount of ABS can be increased to maintain an appropriate rubber content, and the size of the ABS resin domain also increases due to increase of SAN content in ABS. In this case, the domain can be decreased by changing extrusion/injection molding conditions. In addition, the ABS resin having a high content of rubber (grafted ABS resin) can be mixed with PC in order to inhibit the formation of SAN domains as much as possible. Namely, SAN is graft polymerized to interfaces of rubber particles. When the ABS resin having a high content of rubber is mixed with PC, the ABS resin can have improved dispersibility. However, the ABS resin can be partially present in an aciniform shape according to molding conditions, size and content of rubber in the ABS resin, and the SAN component ratio and structure in a grafted layer, thereby deteriorating the quality of the grafted resin.